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Drafting for MPG - Some Thoughts

Discussion in 'Prius c Fuel Economy' started by Mr Incredible, Apr 21, 2012.

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  1. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    I draft big trucks on occasion. Nothing like NASCAR wanna-be's, but I do it when an opportunity arises and I see that the coast is clear.

    However, some rules apply:

    -Never draft dangerously.
    -NEVER bother the big truck driver.
    -Don't get greedy.
    -It isn't always a good thing to do. Know when to say when.

    Tips:

    -Use the small screen 5 min consumption tool to watch the current mpgs. The current mpgs will fluctuate up and down with the wind and will rise precipitously when you enter The Pocket.
    -There will be some buffeting as you approach the pocket. This is where the air from either side of the truck merge again.
    -The position of the pocket will vary with wind speed and direction. It may be behind the truck, or to either side of it. You may not be able to enter it. It may be too close for safety. Or, it may be much farther back than you imagined.
    -Trucks usually travel approximately the same speed for extended periods. They speed up and slow down according to hills and wind. Often, you can use your cruise control and adjust one/two mph at a time to keep in the pocket.
    -Do not get closer than 10 car lengths or close enough to where you lose sight of the trucks mirrors.
    -Do not bother the driver or freak him/her out. You are a partner on the highway, and the driver already has enough to do without worrying about some crazy hyper-miler.

    The pocket is a fickle thing. A will-o-the-wisp. It will occasionally tolerate you, but it can also lure you to your doom. Always be wary and attentive.

    Did I mention not to bother the driver?

    I don't advocate drafting anything, anywhere. But if you think you're good enough to try, try to do it correctly and with the truck driver foremost in your thoughts.

    Some experts have different ideas. These are mine. YMMV. Avoid where prohibited.

    Happy motoring.
  2. F8L

    F8L Protecting Habitat & AG Lands

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    One ancillary benefit of drafting or at least following a big rig is that they can act as a blocker for faster flowing traffic. If you want to drive at the speed limit or just below it then pop in behi d a big rig, leaving enough room between you both to be safe, and cruise at their speed. The traffic behind you would be forced to go around the big rig anyway so it's not like YOU are the one slowing traffic down. This is about the only way I can drive at 60mph without upsetting everyone on the freeway around me. :)
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  3. bisco

    bisco cookie crumbler

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    that's exactly what i like to do, great minds think alike!
  4. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

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  5. maverickf

    maverickf New Member

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    F8L, exactly what I do, I follow the big rigs so traffic behind doesn't blame on me slowing down the flow. :D
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  6. dig4dirt

    dig4dirt Bang-ging SuperWhite

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    10 car lengths?
    Is that just a warning to persuade?

    We used to draft way back when we were young and dumb, but
    it was inches away from the truck...that pocket would literally pull you
    up a steep incline, no problem.
    Typically it was my friend that would do this, in a gas saving crunch for dumb reasons.

    I was always told by my father to always keep one car distance (10 feet est) for
    each 10 mph. i.e. 6 car lengths for 60 mph.

    Anyway, driving the Prius 3 yesterday on the highway I came up on a
    big rig and for giggles, I put it on cruise and closed in.
    I am not sure if it was side wind or what, but the Prius just shuttered
    and was a bit scary (with 2 kids in the back)
    It didnt seem that I had lost control of any steering or braking,
    but each time a car passed, it made feeling of the Prius..
    a cheap light piece of crap. (for loss of words)
    So I brought it in closer to the truck (up to about 2 car lengths)
    and then eased back. Same deal.
    I dont know if I couldnt find the pocket, or if it was due to side wind,
    but I didnt try anymore.
    Over all the total time was just a few minutes at most.

    Of course I didnt do anything dangerous, but never experienced it act that
    way. I will take it as side wind, not anything the truck or Prius was doing.
  7. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    I won't be shy here. IMO, drafting within two car lengths is plain stupid. Doing it with kids in the car is criminal. I think the key phrase was something about being young and dumb.

    As I said the post, other experts have their own opinion but this is mine.
  8. jsfabb

    jsfabb Active Member

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    Use the 1 Min Consumption Chart, it gives you 5 times the feedback. I call it my 1 Minute Report Card. You get to it by just holding down the DISP button. It will toggle between the two every time you release and press again.
  9. jsfabb

    jsfabb Active Member

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    Your estimate is way off, because the Prius C is 13', so 10 lengths is 130'.

    Personally (Prius 3) I keep about 1-1.25 seconds behind a larger vehicle. I find that the difference in the 1 Min Consumption Chart is about 15-20 MPGs better. At 60 mph for each second it's about 88'.
  10. fuzzy1

    fuzzy1 Senior Member

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    :eek:
    Please be aware that the Two Second Rule demands at least 176 feet at this speed.

    In many areas this rule doesn't fit the reality of urban congestion, but other areas have plenty of room to obey it.
  11. ProximalSuns

    ProximalSuns Senior Member

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    It's technically impossible to draft a big rig at high speed safely.

    To be safe, you are too far back to get any drafting effect. To get any effect, way too close for safe braking. Add in chance of rocks or road debris coming at you too fast to avoid.

    Better to buy a fuel efficient car and drive it safely.
  12. Son of Gloin

    Son of Gloin Member

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    On those RARE occasions that I draft big-rigs - they're usually going somewhat faster than I care to drive! - I tend to be at least 5 or 6 car lengths back, Mithril is set on "cruise control", I adjust speed with the "cruise control lever" ... AND ... my foot is ALWAYS positioned ever-so-lightly on the brake pedal, just in case! Even that "far" back - assuming the wind direction is conducive to such tactics - Mithril's mpg will tend to jump 5-to-15 mpg according to the instant read-out. Lastly ... I almost NEVER draft the same rig for more than 10 minutes or so, and I generally take at least a 20 minute break before drafting another one IF another one becomes available.
  13. Son of Gloin

    Son of Gloin Member

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    If the opportunity presents itself, PLEASE feel free to tell drivers of big rigs this. Collectively, "THEY" actually end up spending more time riding MY ass - often at less than 20 feet! - than I do drafting them at 50-to-100 feet.
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  14. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    Sounds impressive, but I disagree. That's fine. Everyone has an opinion.

    If the pocket falls within my safety parameters, I'm drafting. If it doesn't, I'm not. Pretty simple.
  15. ProximalSuns

    ProximalSuns Senior Member

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    No it is a fact that you cannot meet safety parameters and draft a big rig at high speed.

    It is your opinion that you wish to operate unsafely to save a few cents on gasoline.

    Two different things.
  16. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    Please explain, if you would, why there are no parameters for safe drafting.

    If the pocket is back 20 carlengths, or enough of the pocket to show improvement, is not 20 carlengths sufficient? 30? 50? What is the minimum distance we should put between ourselves and any truck. Or car, or SUV, or motorcycle?
  17. nubomb

    nubomb Junior Member

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    I get a kick out of reading posts about safe following distances...I must be living in bazzaro world....2 second rule, car lengths per 10 mph. Try that by me on a major highway, commuting to/from work, and that 200 foot cushion is quickly reduced with 15 cars cutting you off. Right lane is no better with exits every mile and random people driving 10 mph under the posted limit and others 10 over (right up your rearend).

    Forget about drafting, I'm just trying to keep out of other people's blind spots and making sure I have a move other than using my breaks.
  18. ProximalSuns

    ProximalSuns Senior Member

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    At 55-65 mph you are 250-300 feet back and well out of draft.
  19. Mr Incredible

    Mr Incredible Chance favors the prepared mind.

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    That's pretty unrealistic most days, most highways, but do as you wish. I don'think I've ever met anyone so safety intent.
  20. ProximalSuns

    ProximalSuns Senior Member

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    You can try this website for suggested safe distances.

    If you more the 100 feet back, there's not much drafting effect and at 55 mph, 240 feet is suggested safe distance.
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